1 /* 2 * SoftDog 0.07: A Software Watchdog Device 3 * 4 * (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>, 5 * All Rights Reserved. 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 10 * 2 of the License, or (at your option) any later version. 11 * 12 * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide 13 * warranty for any of this software. This material is provided 14 * "AS-IS" and at no charge. 15 * 16 * (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk> 17 * 18 * Software only watchdog driver. Unlike its big brother the WDT501P 19 * driver this won't always recover a failed machine. 20 * 21 * 03/96: Angelo Haritsis <ah@doc.ic.ac.uk> : 22 * Modularised. 23 * Added soft_margin; use upon insmod to change the timer delay. 24 * NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate 25 * minors. 26 * 27 * 19980911 Alan Cox 28 * Made SMP safe for 2.3.x 29 * 30 * 20011127 Joel Becker (jlbec@evilplan.org> 31 * Added soft_noboot; Allows testing the softdog trigger without 32 * requiring a recompile. 33 * Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT. 34 * 35 * 20020530 Joel Becker <joel.becker@oracle.com> 36 * Added Matt Domsch's nowayout module option. 37 */ 38 39 #include <linux/module.h> 40 #include <linux/moduleparam.h> 41 #include <linux/types.h> 42 #include <linux/timer.h> 43 #include <linux/miscdevice.h> 44 #include <linux/watchdog.h> 45 #include <linux/fs.h> 46 #include <linux/notifier.h> 47 #include <linux/reboot.h> 48 #include <linux/init.h> 49 #include <linux/jiffies.h> 50 #include <linux/uaccess.h> 51 52 #define PFX "SoftDog: " 53 54 #define TIMER_MARGIN 60 /* Default is 60 seconds */ 55 static int soft_margin = TIMER_MARGIN; /* in seconds */ 56 module_param(soft_margin, int, 0); 57 MODULE_PARM_DESC(soft_margin, 58 "Watchdog soft_margin in seconds. (0 < soft_margin < 65536, default=" 59 __MODULE_STRING(TIMER_MARGIN) ")"); 60 61 static int nowayout = WATCHDOG_NOWAYOUT; 62 module_param(nowayout, int, 0); 63 MODULE_PARM_DESC(nowayout, 64 "Watchdog cannot be stopped once started (default=" 65 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 66 67 #ifdef ONLY_TESTING 68 static int soft_noboot = 1; 69 #else 70 static int soft_noboot = 0; 71 #endif /* ONLY_TESTING */ 72 73 module_param(soft_noboot, int, 0); 74 MODULE_PARM_DESC(soft_noboot, 75 "Softdog action, set to 1 to ignore reboots, 0 to reboot " 76 "(default depends on ONLY_TESTING)"); 77 78 /* 79 * Our timer 80 */ 81 82 static void watchdog_fire(unsigned long); 83 84 static struct timer_list watchdog_ticktock = 85 TIMER_INITIALIZER(watchdog_fire, 0, 0); 86 static unsigned long driver_open, orphan_timer; 87 static char expect_close; 88 89 90 /* 91 * If the timer expires.. 92 */ 93 94 static void watchdog_fire(unsigned long data) 95 { 96 if (test_and_clear_bit(0, &orphan_timer)) 97 module_put(THIS_MODULE); 98 99 if (soft_noboot) 100 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n"); 101 else { 102 printk(KERN_CRIT PFX "Initiating system reboot.\n"); 103 emergency_restart(); 104 printk(KERN_CRIT PFX "Reboot didn't ?????\n"); 105 } 106 } 107 108 /* 109 * Softdog operations 110 */ 111 112 static int softdog_keepalive(void) 113 { 114 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ)); 115 return 0; 116 } 117 118 static int softdog_stop(void) 119 { 120 del_timer(&watchdog_ticktock); 121 return 0; 122 } 123 124 static int softdog_set_heartbeat(int t) 125 { 126 if ((t < 0x0001) || (t > 0xFFFF)) 127 return -EINVAL; 128 129 soft_margin = t; 130 return 0; 131 } 132 133 /* 134 * /dev/watchdog handling 135 */ 136 137 static int softdog_open(struct inode *inode, struct file *file) 138 { 139 if (test_and_set_bit(0, &driver_open)) 140 return -EBUSY; 141 if (!test_and_clear_bit(0, &orphan_timer)) 142 __module_get(THIS_MODULE); 143 /* 144 * Activate timer 145 */ 146 softdog_keepalive(); 147 return nonseekable_open(inode, file); 148 } 149 150 static int softdog_release(struct inode *inode, struct file *file) 151 { 152 /* 153 * Shut off the timer. 154 * Lock it in if it's a module and we set nowayout 155 */ 156 if (expect_close == 42) { 157 softdog_stop(); 158 module_put(THIS_MODULE); 159 } else { 160 printk(KERN_CRIT PFX 161 "Unexpected close, not stopping watchdog!\n"); 162 set_bit(0, &orphan_timer); 163 softdog_keepalive(); 164 } 165 clear_bit(0, &driver_open); 166 expect_close = 0; 167 return 0; 168 } 169 170 static ssize_t softdog_write(struct file *file, const char __user *data, 171 size_t len, loff_t *ppos) 172 { 173 /* 174 * Refresh the timer. 175 */ 176 if (len) { 177 if (!nowayout) { 178 size_t i; 179 180 /* In case it was set long ago */ 181 expect_close = 0; 182 183 for (i = 0; i != len; i++) { 184 char c; 185 186 if (get_user(c, data + i)) 187 return -EFAULT; 188 if (c == 'V') 189 expect_close = 42; 190 } 191 } 192 softdog_keepalive(); 193 } 194 return len; 195 } 196 197 static long softdog_ioctl(struct file *file, unsigned int cmd, 198 unsigned long arg) 199 { 200 void __user *argp = (void __user *)arg; 201 int __user *p = argp; 202 int new_margin; 203 static const struct watchdog_info ident = { 204 .options = WDIOF_SETTIMEOUT | 205 WDIOF_KEEPALIVEPING | 206 WDIOF_MAGICCLOSE, 207 .firmware_version = 0, 208 .identity = "Software Watchdog", 209 }; 210 switch (cmd) { 211 case WDIOC_GETSUPPORT: 212 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0; 213 case WDIOC_GETSTATUS: 214 case WDIOC_GETBOOTSTATUS: 215 return put_user(0, p); 216 case WDIOC_KEEPALIVE: 217 softdog_keepalive(); 218 return 0; 219 case WDIOC_SETTIMEOUT: 220 if (get_user(new_margin, p)) 221 return -EFAULT; 222 if (softdog_set_heartbeat(new_margin)) 223 return -EINVAL; 224 softdog_keepalive(); 225 /* Fall */ 226 case WDIOC_GETTIMEOUT: 227 return put_user(soft_margin, p); 228 default: 229 return -ENOTTY; 230 } 231 } 232 233 /* 234 * Notifier for system down 235 */ 236 237 static int softdog_notify_sys(struct notifier_block *this, unsigned long code, 238 void *unused) 239 { 240 if (code == SYS_DOWN || code == SYS_HALT) 241 /* Turn the WDT off */ 242 softdog_stop(); 243 return NOTIFY_DONE; 244 } 245 246 /* 247 * Kernel Interfaces 248 */ 249 250 static const struct file_operations softdog_fops = { 251 .owner = THIS_MODULE, 252 .llseek = no_llseek, 253 .write = softdog_write, 254 .unlocked_ioctl = softdog_ioctl, 255 .open = softdog_open, 256 .release = softdog_release, 257 }; 258 259 static struct miscdevice softdog_miscdev = { 260 .minor = WATCHDOG_MINOR, 261 .name = "watchdog", 262 .fops = &softdog_fops, 263 }; 264 265 static struct notifier_block softdog_notifier = { 266 .notifier_call = softdog_notify_sys, 267 }; 268 269 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 " 270 "initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n"; 271 272 static int __init watchdog_init(void) 273 { 274 int ret; 275 276 /* Check that the soft_margin value is within it's range; 277 if not reset to the default */ 278 if (softdog_set_heartbeat(soft_margin)) { 279 softdog_set_heartbeat(TIMER_MARGIN); 280 printk(KERN_INFO PFX 281 "soft_margin must be 0 < soft_margin < 65536, using %d\n", 282 TIMER_MARGIN); 283 } 284 285 ret = register_reboot_notifier(&softdog_notifier); 286 if (ret) { 287 printk(KERN_ERR PFX 288 "cannot register reboot notifier (err=%d)\n", ret); 289 return ret; 290 } 291 292 ret = misc_register(&softdog_miscdev); 293 if (ret) { 294 printk(KERN_ERR PFX 295 "cannot register miscdev on minor=%d (err=%d)\n", 296 WATCHDOG_MINOR, ret); 297 unregister_reboot_notifier(&softdog_notifier); 298 return ret; 299 } 300 301 printk(banner, soft_noboot, soft_margin, nowayout); 302 303 return 0; 304 } 305 306 static void __exit watchdog_exit(void) 307 { 308 misc_deregister(&softdog_miscdev); 309 unregister_reboot_notifier(&softdog_notifier); 310 } 311 312 module_init(watchdog_init); 313 module_exit(watchdog_exit); 314 315 MODULE_AUTHOR("Alan Cox"); 316 MODULE_DESCRIPTION("Software Watchdog Device Driver"); 317 MODULE_LICENSE("GPL"); 318 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 319